San Diego homeowners face a great choice when space runs out: build an ADU or add on to the existing home. If you are weighing an ADU in San Diego against a Home Addition San Diego project, the right path depends on how you plan to use the space, your budget, timeline, and the local rules that shape what you can build. This guide unpacks costs, permitting, and practical considerations so you can move forward with confidence.
ADU San Diego vs Home Addition San Diego: Key Differences
An Accessory Dwelling Unit San Diego project creates a second, independent dwelling on the same lot. A home addition increases square footage inside the primary home. Both increase livability and can boost San Diego property value, but they function differently day to day.
| Factor | ADU (Accessory Dwelling Unit) | Home Addition |
|---|---|---|
| Definition | Separate dwelling with kitchen, bath, sleeping area | Additional rooms attached to the main house |
| Use Case | Rental income, in-law unit San Diego, multigenerational living | Expand primary living spaces: bedrooms, kitchen, office |
| Privacy | High privacy with a separate entrance | Integrated with the main home |
| Rentability | Often rentable as long-term housing | Typically not separately rentable |
| Cost Pattern | Complete small home; more systems per square foot | Shares systems with existing home; lower cost per square foot |
| Impact On Value | Adds versatile unit; potential rental income San Diego | Improves layout and livability; resale appeal |
| Parking | Rules vary; some exemptions near transit | May need to maintain required on-site parking |
| Timeline | Permitting can be streamlined; construction similar to small home | Structural tie-ins can add complexity; interior disruption |
Cost, Timeline, And Value: What To Expect
ADU vs Home Addition Cost San Diego
Budgets vary with size, site constraints, utilities, and finishes. The ranges below reflect typical 2024–2025 design-build pricing seen across the county and are for planning only. Request local bids to confirm your exact costs.
- Garage Conversion ADU San Diego: Approximately $120,000 to $220,000 for a standard two-car conversion, assuming adequate structure, utility access, and code-compliant ceiling height.
- Detached ADU (New Build): Approximately $220,000 to $400,000+ for 400–800 sq ft; larger units and complex sites can exceed $450,000.
- Junior ADU (JADU): Interior conversion with a small kitchenette; often $60,000 to $150,000 depending on plumbing path and configuration.
- Room Addition San Diego (Single Story): Roughly $250 to $450 per sq ft for bedrooms, family rooms, or expanded kitchens, depending on structural changes and finishes.
- Second Story Addition: Often $300 to $550 per sq ft due to structural upgrades, stairs, and roofing changes.
Per-square-foot numbers for additions can appear lower because the project shares systems with the main house. ADUs look higher per square foot because they require a full set of independent systems (kitchen, bath, water heater, sometimes separate meters).
Rental Income And San Diego Property Value
An ADU can deliver long-term rental income that helps offset mortgage costs and diversify your financial plan. Many owners also create a future-proof in-law unit San Diego families can use for aging parents, adult children, or caregivers. A well-executed home addition, by contrast, often boosts resale appeal, improves daily function, and may increase appraised value without adding a separate dwelling. Your best move depends on whether you want monthly income, a lifestyle upgrade, or both.
Timeline To Plan For
- Design and Permitting: 2 to 6 months for either path, depending on scope, revisions, and whether you are in the Coastal Overlay Zone.
- Construction: 3 to 8 months for an ADU; 2 to 6 months for a typical addition; complex second stories can run longer.
Factor in utility lead times, HOA architectural reviews, and potential structural upgrades on older homes.
San Diego Accessory Dwelling Unit Rules And Permitting
San Diego ADU Permit Requirements
Plan on submitting a complete package: site plan, floor plans, elevations, structural calculations, Title 24 energy documentation, and any stormwater requirements. Coastal parcels may require a coastal review. Some projects qualify for streamlined processing. Verify submittal standards with the City before you begin; you can review city handouts and checklists here: City ADU resources.
What Are ADU Setback Rules San Diego?
Many properties follow state-aligned standards that allow reduced side and rear setbacks for ADUs, often as little as four feet, plus height and lot coverage limits. Specifics vary by zoning, lot size, and whether you are in special overlays or fire zones. Always confirm current rules and any design guidelines with the City of San Diego before finalizing plans: San Diego building codes.
Garage Conversion ADU San Diego
Converting a garage can be one of the fastest ways to create an ADU. Key checkpoints include structural integrity, slab moisture and insulation strategy, fire separation from the main house, required ceiling heights, egress windows, natural light and ventilation, and safe routing of plumbing and electrical. Off-street parking replacement may not be required in some cases, especially near transit, but verify the latest parking rules for your address.
San Diego Accessory Dwelling Unit Rules To Watch
- Types: Detached ADU, attached ADU, and Junior ADU options exist, each with unique size and kitchen requirements.
- Ownership: Owner-occupancy requirements have evolved; rules differ for ADUs and JADUs, and policies can change. Confirm before you plan for rental income.
- Utilities: Separate meters are sometimes optional. Coordinate early with utilities to understand fees and timing.
- Design Standards: Height, lot coverage, and architectural compatibility may apply. Check community plan overlays.
Home Addition Regulations And Design Tips
Do I Need A Permit For A Home Addition In San Diego?
Yes. Nearly all additions require permits for structural, electrical, plumbing, and mechanical work. Coastal, brush, and historical overlays can add steps, and HOA approvals may apply. A clear set of plans and early pre-submittal coordination help control timelines.
Second Story Addition San Diego Regulations
Second stories often require foundation evaluation, shear upgrades, and careful stair and egress planning. Height limits, setbacks, and neighborhood design guidelines can influence massing, windows, and privacy. If you are in the Coastal Overlay Zone or a planned community, allow extra time for discretionary reviews. A structural engineer should assess load paths and existing framing before you finalize the concept.
How To Choose: A Simple Decision Framework
- Primary Goal: If rental income or an independent suite is a must, lean toward an ADU. If you want better daily flow, more bedrooms, or a larger kitchen, consider a home addition.
- Privacy And Lifestyle: ADUs offer separation and flexibility for multigenerational living. Additions integrate seamlessly with your current layout.
- Budget Strategy: Additions may cost less per square foot. ADUs can offset their higher total cost with rent.
- Zoning Reality: Some lots favor one option due to setbacks, lot coverage, or coastal rules.
- Timeline And Disruption: ADUs can be built outside the main home, reducing disruption; additions may impact daily living during construction.
- Future Resale: Consider buyer demand in your neighborhood for an accessory dwelling unit San Diego buyers can rent versus a larger main residence.
Step-By-Step: From Idea To Permit
- Site Check: Verify zoning, overlays, setbacks, and utility access. A quick zoning report or consultation can prevent dead ends.
- Program And Budget: Define who will use the space, must-have features, and a budget range.
- Feasibility Study: Measure the home and lot, review San Diego building codes, and confirm constraints such as height limits and parking.
- Concept Design: Develop test-fit layouts for both options (ADU and addition). Compare estimated costs and value impacts.
- Pre-Submittal Review: Meet the City or use online intake to clarify requirements and streamline your submittal.
- Construction Documents: Complete architectural plans, structural calculations, energy compliance, and any reports.
- Permitting: Submit, respond to plan check comments, and secure approvals.
- Bidding And Financing: Obtain apples-to-apples bids and explore financing such as HELOC, cash-out refi, or renovation loans. See financing options.
- Build: Maintain a clean jobsite, clear communication, and scheduled inspections to keep momentum.
Pros And Cons At A Glance
ADU (Granny Flat San Diego)
- Pros: Rental income potential, privacy for guests or family, flexible long-term use, can enhance overall property utility.
- Cons: Higher total cost than a small addition, more complex utility planning, strict design rules on some lots.
Home Addition
- Pros: Improves daily living inside the main home, typically lower cost per square foot, simpler utility integration.
- Cons: Limited rental potential, more disruption during construction, can be constrained by structure and layout.
Answers To Common Questions
What is an ADU in San Diego?
An ADU is a self-contained secondary residence on the same lot as a primary home. It has a kitchen, bathroom, and sleeping area. In San Diego, ADUs include detached units, attached units, and interior conversions such as JADUs. They are commonly called a granny flat San Diego homeowners build for family or rental income.
Is an ADU or home addition better in San Diego?
If you want rental income or a private suite for multigenerational living, an ADU is typically stronger. If you need larger living areas or bedrooms connected to your main home, choose a home addition. Evaluate zoning, cost, privacy, and long-term goals, then pick the option that aligns with your plan.
How much does an ADU cost in San Diego?
As a planning range, garage conversions often run $120,000 to $220,000, detached ADUs about $220,000 to $400,000+, and JADUs about $60,000 to $150,000. Actual costs depend on size, site complexity, and finish level.
Do I need a permit for a home addition in San Diego?
Yes. Almost all home additions require permits for structural, electrical, plumbing, and mechanical work. Additional approvals may apply in coastal or special overlay areas and in HOA communities.
What are ADU setback rules San Diego?
State-aligned standards often allow reduced side and rear setbacks for ADUs, commonly around four feet, with height and lot coverage limits. Always confirm your parcel-specific rules with the City before final design.
Final Recommendation For Your San Diego Home
If your top priority is income flexibility and privacy, an ADU is hard to beat. If you are focused on day-to-day living and improving the flow of your existing home, a targeted addition can deliver high value. Start with a feasibility review of both paths, compare total project cost versus expected benefits, and run numbers for rent, carrying costs, and resale. A short consult with a local design-build team or planning professional can save months later. When you are ready, gather your wish list, recent survey or site plan, photos of the property, and any HOA guidelines, then schedule a feasibility call here: book a consultation.